Indian Scientists Devise Low-Cost Method To Secure Long-Distance Communication By Overcoming Distortions

A team of Indian scientists have devised a low-cost method to secure long-distance communication by overcoming distortions.

Scientists at the Quantum Information and Computing (QuIC) lab at the Raman Research Institute (RRI), Bengaluru have developed a method to overcome the distortion caused by photon-polarisation due to satellite movement and scrambling of polarisation in optical fibers.

This breakthrough allows for secure long-distance communication without the need for expensive conventional active-polarisation tracking devices.

In today's digital age, the security of personal data is a major concern. With the increasing use of online services and payment gateways, sensitive information such as Aadhaar and PAN numbers, phone numbers, and photos are at risk of being compromised.

Recognizing the need for secure communication in various domains, including defense and national security, the scientists at QuIC lab set out to find a solution, according to Ministry of Science and Technology.

The QuIC lab has been working on developing a secure Quantum Key Distribution (QKD) protocol, aiming to establish a globally secure quantum network.

This recent advancement is part of their ongoing quantum experiments using satellite technology, in collaboration with the Indian Space Research Organisation (ISRO).

To achieve secure communication using QKD, the researchers proposed an approach based on the BBM92 QKD protocol, which utilises entanglement.

Unlike traditional methods that require complex active-polarization tracking, their approach incorporates feedback-based mechanisms for real-time polarisation tracking. This eliminates the need for costly devices and offers a cost-effective solution.

Professor Urbasi Sinha, head of the QuIC lab, stated that their approach uses optimisation methods to balance the key rate, quantum-bit-error-rate (QBER), and key symmetry, ensuring minimal eavesdropping probability. This cost-effective solution requires no additional resources.

The researchers achieved a fidelity of 94 percent in their entangled state using Quantum State Tomography. Even with lower fidelity, down to 10 percent, the protocol maintained high performance.

Sourav Chatterjee, former project scientist under the QuEST research grant, explained that the protocol's implementation is independent of local polarization rotation. In the classical post-processing step, their optimization methods maximize the key rate while keeping the QBER below the secure threshold of 11 per cent and ensuring a balanced key symmetry.